Major routes were multiples of 10, with 10, 20, and 90 running east/west, 30, 40, 50, 70, and 80 running north/south, and 60 running as a diagonal route. These cross-state routes were used as a basis for numbering the two-digit roads that served as the major city-city connectors. For example, NC 90 used to run along modern US 64, which explains the multiple "90s" that branch off US 64 today (NC 9, NC 97 and NC 98). Three-digit numbered roads were less important spurs off the two-digit roads and often served as rural connectors. These were numbered in a scheme opposite of the U.S. and Interstate auxiliary routes; the spur routes received an extra "ones" digit instead of an extra "hundreds" digit. The first spur received the number "xx1" and the second received "xx2", where xx is the parent route number. This explains the predomination of such routes as 751, 191, 561, and the relatively few "xx0" routes (which would be the 10th assigned spur route ... few parent routes would have spurs numbered this high). In 1933-34 many roads were renumbered to eliminate conflicts with the U.S. highways now crisscrossing the state. Some numbers (50, 90), which had become effectively U.S. routes (1 and 64 respectively) were moved or eliminated while others that conflicted with established U.S. route numbers in the state were changed to non-conflicting numbers. This seems to have been done without regard to the earlier numbering system, as were all future additions to the state highway system, which is where the modern "lack of any system" system came to be. In 1937, several routes were renumbered to be contiguous with South Carolina routes, and in 1940 the same happened with Virginia. No effort has ever been made to match up with Tennessee or Georgia routes, but most cross-border numbered roads along this area are already U.S. highways anyway. In 1961, the routes that conflicted with Interstates were renumbered. Highway renumbering has since been sporadic, with most being place-holders for a future Interstate route (i.e. NC 752 and NC 295). One exception being a state law passed in 2002 swapping the highway numbers of NC 136 and NC 3; the reason was in tribute to Dale Earnhardt who died in the 2001 Daytona 500, who drove the number #3 Goodwrench Chevrolet and lived in Kannapolis. See also North Carolina State Ports Authority North Carolina Ferry System North